Before taking up this position in 2009, he was a Washington-based public service broadcasting manager. He has also worked as a journalist, magazine publisher and business writer, and in the field of economic policy development. He is perhaps best known for co-writing the book Dow 36,000 (published 1999), in which he predicted that the Dow Jones Industrial Average would approximately triple in value to 36,000 points by early 2005.

While a student at Harvard, he served as managing editor of The Harvard Crimson.[3] After graduation, he took a job as a Sunday writer for the Boston Herald Traveler. In 1971, he became editor and publisher of The Advocate of Provincetown, Mass..

From 1987 until 1993, Glassman was part owner and editor of Roll Call.[4] He and his partner, Arthur Levitt Jr., sold the company to The Economist.

In 2000 he founded Tech Central Station (now TCS Daily), an online magazine.[4]

Between 1993 and 2004, he wrote a syndicated column for the Washington Post business section and the International Herald Tribune.[5]

Glassman has also worked in television. He was moderator of CNN's “Capital Gang Sunday” from 1995 to1998.[4] During this time he also hosted PBS's weekly "TechnoPolitics."[4] From February 2010 to June 2012, he hosted “Ideas in Action,” a weekly PBS series on public policy issues.[5]

From 1996 to 2008, Glassman was a senior fellow at the American Enterprise Institute in Washington, D.C.[5] While there, from 2005 to 2007, he founded and served as editor in chief of The American, the American Enterprise Institute's bimonthly magazine of business and economics.[6]

In 2003, Glassman served on the U.S. government's Advisory Board on Public Diplomacy in the Arab and Muslim World.[6]

On December 11, 2007, Glassman was nominated by President George W. Bush to replace Karen Hughes as the undersecretary of state for public diplomacy and public affairs.[2] He served in the position from June 2008 to January 2009, leading the governmentwide international strategic communications effort. Among his accomplishments at the State Department was bringing new Internet technology to bear on outreach to foreign publics, an approach he christened “Public Diplomacy 2.0.”[5] In an interview in 2009, he put forward a case that in the long run the Iraq War will prove to have been a positive decision, saying that it will be ultimately "beneficial to the war of ideas in the sense that a functioning democracy that we hope will be stable and prosperous now exists in the Middle East, and is showing other nations and other people what a democracy looks like."

Newsweek said about him: “James K. Glassman, as they say in Washington, gets it. The under secretary of state for public diplomacy has been on the job for only six months, but he has already scored small successes in the U.S. effort to win over ‘hearts and minds’ in the Muslim world, a hard sell if ever there was one. . . . Glassman has finally figured out how to sell the American idea abroad.”[7]

He continued to serve as a governor of the BBG, representing the secretary of state, during his time as under secretary.[5]

On September 3, 2009, Glassman was named founding executive director of the George W. Bush Institute, a public policy institute dedicated to research and action in education, global health, human freedom, and economic growth.[8] The Institute is part of the George W. Bush Presidential Center, which also includes a presidential library and museum on the campus of Southern Methodist University in Dallas, Texas.[5]

Additionally, Glassman is one of 21 members of the Investor Advisory Committee of the Securities and Exchange Commission, established in April 2012 as part of the Dodd-Frank law, and the advisory board of America Abroad Media.[9]

His first book, Dow 36,000, was published in 1999, near the peak of the late-1990s stock market bubble.

The book was later criticized by Washington Post reporter Carlos Lozada, who asked, “You don't feel the need to apologize to someone who read your book, went in and got creamed?” Glassman replied, “Absolutely not.”[10] Nobel laureate Paul Krugman argued on his faculty website that the book contained basic arithmetic errors and was 'very silly'.[11] Economist and blogger Nate Silver described the book as 'charlatanic' and suggested on empirical grounds that the authors had failed to notice that the time of writing stock prices were 'as overvalued as at literally any time in American history'.[12]

In 2011, in his third book, Safety Net: The Strategy for De-Risking Your Investments in a Time of Turbulence, he wrote “I was wrong” about his predictions in Dow 36,000, noting that the Dow Jones only went up 20 percent since publication of the book and returns during the intervening years were only “a few piddling percentage points.”[10] In Safety Net, he argued that “the world has changed” over the past decade; that the U.S. relative economic position had declined and that the risk of catastrophic events had increased. He warned investors to adopt a new definition of risk, moving beyond the notion of financial volatility.[13]

In March 2013, he reverted to his former position, stating in an article for Bloomberg L.P. that while he had underestimated the level of volatility in world events, he believed that reaching 'Dow 36,000' was still possible within less than a decade with the right policies.[14]Gawker Media, in an article on his predictions, described him as having written 'the most hilariously wrong investment book of all time'.[15]

His second book, The Secret Code of the Superior Investor: How to Be a Long-Term Winner in a Short-Term World, was published by Three Rivers Press in December 2002. The book focused on the construction of a solid personal portfolio. It offered advice for finding the best individual stocks and mutual funds even in uncertain times and volatile markets.

At the heart of Glassman's “secret code” is the belief that stocks are the best long-term bet there is. The trick is finding solid companies to invest in and then sticking with those companies through thick and thin.[16] Glassman wrote a weekly and twice-weekly investment column for The Washington Post from 1993 to 2004 and since then has written a monthly column for Kiplinger’s Personal Finance.